The present invention relates to abrasion-resistant, durable material handling hose for use in industrial applications, and particularly to acid chemical and/or petroleum product bulk transfer hose having an improved abrasion-resistant cover element.
Material handling hose for use in industrial applications including tanker truck transfer, storage tank transfer, ship and/or barge transfer, and for conveying materials including acid chemicals and petroleum products, such as gasoline, diesel fuel, etc., commonly include an elastomeric, thermoplastic or plastic inner liner or tube, a suitable reinforcement member, and a suitable cover to provide flexibility and/or ease of handling. The inner liner may be of a permeable, semi-permeable or substantially chemical impermeable variety, depending in general on the material to be conveyed. For acid chemical applications, highly chemical resistant polyfluorocarbon thermoplastics or other substantially chemical impermeable materials are generally employed to minimize the risk of environmental contamination by the conveyed fluid. For petroleum product applications, semi-permeable materials including acrylonitrile butadiene rubber (xe2x80x9cNBRxe2x80x9d) are advantageously employed as the inner liner material in order to allow any highly volatile material remaining in the hose between transfer operations to vent through the hose materials to the outside environment in order to reduce or eliminate pooling of such material within the hose.
Because the bulk transfer applications to which the present invention is particularly directed frequently involve dragging lengths of such hose across abrasive flooring materials on a regular basis, wear of the cover element and consequent exposure of the inner hose materials is a significant problem. To address this problem, it has been suggested to increase the relative thickness of the cover element, in order to allow for some wear thereof without the risk that inner hose layers will be compromised within a normal service period. This solution is not completely satisfactory because even without such additional cover thickness, this type of hose, typically having an inner diameter of from about 1 to about 4 inches (2.5 to 10.2 cm) or even greater, is generally quite heavy and may be awkward to handle. It is commonplace that more than one operator is needed to drag such hose from one location to another, or to bring it to the point of operation. The incorporation of additional cover material would is thus likely serve to exacerbate the weight and handling difficulties of such hose.
Alternatively, it has been suggested for some applications, e.g., hydraulic hose, to add an abrasion resistant veneer or film onto the outer surface of the aforementioned cover, such that that xe2x80x9ccoverxe2x80x9d actually becomes an intermediate layer between the inner tube and reinforcement member on one side, and the outer veneer or film on the other. The abrasion resistant outer veneer is advantageously formed of a plastics material having a relatively low coefficient of friction compared to the intermediate layer, and may be applied for example via known methods in a spiral-type configuration about the hose, such that it completely covers the outer surface of the intermediate layer of the hose. The lower effective coefficient of friction of the hose results in decreased wear and consequent reduction in hose damage over unprotected hose.
This proposed solution does not satisfactorily resolve the problems associated with material handling hose of the type presently contemplated for at least two reasons. First, the hose having a low coefficient of friction cover is slippery and therefore difficult to establish and maintain a grip upon or otherwise handle. This is particularly troublesome since as noted, such hose may be quite heavy. This combination of characteristics would result in a material handling hose which is not only difficult to handle due to the increased stiffness of the typically plastics cover element, cumbersome and relatively expensive to operate (in that two operators may be needed to safely handle it), it could make handling the hose more dangerous as well. The contents may be corrosive, toxic, flammable or otherwise hazardous, and the tendency for the operators to lose their grip and cause a chemical spill would likely increase due to the effective lower coefficient of friction compared to hose without such cover element.
Second, if such hose is used to convey highly volatile materials, i.e., materials containing about 25% or more volatile compounds such as petroleum products, some gas or liquid may become entrapped within the semi-permeable hose layers during hose contact. The utilization of a substantially impermeable cover element would in such case potentially create a safety hazard, since such trapped material would not be able to vent through the hose body to the outside environment. Thus, any benefit derived from including a permeable or semi-permeable inner liner in such applications would generally be lost by including the abrasion-resistant cover.
Thus, it is an object of the present invention to overcome the disadvantages of the prior art by providing a material handling hose which exhibits excellent abrasion resistant characteristics, but which nonetheless exhibits good handling characteristics.
It is a further object of the present invention to provide such a hose which allows for maintenance or reduction of the weight of its intermediate layer over prior art configurations without significant detraction from its performance capability or reduction in its expected service life.
It is yet another object of the present invention to provide such a hose incorporating an abrasion-resistant cover element which nonetheless allows for venting of residual gases. It is still a further object of the present invention to provide a material handling hose having a cover element which allows for the incorporation of an identifying design or color, and thus allows for the reduction or elimination of colored rubber stocks.
The present invention provides a material handling hose having a highly abrasion-resistant cover element. The hose comprises a reinforcement layer or member sandwiched between a generally tube-shaped inner liner or layer and a generally tube-shaped intermediate layer, which layers may be formed of the same or different suitable elastomeric, thermoplastic or plastic materials. The hose furthermore comprises the aforementioned abrasion-resistant cover element, which is coaxially disposed about and attached to at least a portion of the intermediate layer, on the side thereof opposite that attached to the reinforcement member. The abrasion-resistant cover element preferably possesses a coefficient of friction lower than that of the intermediate layer, and is preferably substantially impermeable to most common chemicals. The abrasion-resistant cover element moreover does not cover the entire outer surface of the intermediate layer to which it is attached, but instead includes gaps or apertures which are substantially unobstructed, such that the portions of the intermediate layer beneath such apertures are exposed to the outer environment throughout the service lifetime of the hose. The material of the intermediate layer may occupy at least a portion of the cavities formed by such gaps or apertures.